As is well known, outboard motors for use in powering watercraft include an engine powering a water propulsion apparatus of the motor, such as a propeller. These outboard motors have a cowling which encloses the engine.
The motor is generally movably mounted to a stern of a watercraft, and as such, it is desirable that the motor be compact in dimension. Keeping the motor compact reduces air drag and reduces the force necessary to turn or trim the motor. In order that the outboard motor be small in dimension, the engine is arranged to be as compact as possible, and the cowling is sized to fit just around the engine.
The positioning of the engine in the small space defined by the cowling is beneficial when considering the above-stated goals, but creates several problems. A main problem is that the cowling traps significant heat generated by the engine. The high temperatures in the engine may damage components associated with the engine. For example, engine electrical features are often quite sensitive to high temperature conditions.
This heating problem is especially acute when the engine is stopped. In particular, some air normally flows through the cowling when the engine is running, induced by the intake of the engine, the movement of the motor through the air or the like. In addition, the engine may include a liquid cooling system arranged to draw cool water from the body of water in which the motor is operating and deliver it through cooling passages to the engine. This air flow and the flow of liquid coolant stops when the engine stops. In the liquid cooling systems, when the engine stops powering a coolant supply pump, the coolant in the engine cooling passages drains from the engine. At this time, the heat associated with the engine block, head, lubricant and the like is transmitted to the stagnant air in the cowling and the engine accessories and components.
An improved cooling system for an outboard motor having a water propulsion device powered by an internal combustion engine, is desired.